Pressure vacuum breaker downstream of a solenoid?

I am trying to install some kind of backflow device for my small backyard with 6 sprinkler heads. The irrigation system is connected to my water main, i.e. portable water. The sprinklers are on a slope and the solenoid is set up at the front of my house, i.e. 3-4 feet below the sprinklers.

The contractor originally didn't install any back flow devices and now he claims he can add simple PVC checked valve and that would be enough. I originally wants to replace the solenoid with an anti ciphon valve but it can't be set up 6 inches higher than the sprinklers at the front of the house and wires aren't easy to set up in the backyard now all the concrete has been poured. So pressure vacuum breaker is my second option (my contractor said RPZ is an overkill). I was wondering if PVB could be set up after the solenoid, i.e. water main -> solenoid -> PVB -> sprinklers?

Any type of vacuum breaker has to be higher than the highest head or pipe on the sprinkler system. If it takes a "downstream" location to get that elevation difference, you could try that unusual configuration, but in that event, do yourself a favor and use a Wilkins 720A PVB, due to its unique internal configuration resisting premature failure of the internal rubber parts from the continuing on and off pressurizing that a PVB in general was not designed to endure.

Any type of vacuum breaker has to be higher than the highest head or pipe on the sprinkler system. If it takes a "downstream" location to get that elevation difference, you could try that unusual configuration, but in that event, do yourself a favor and use a Wilkins 720A PVB, due to its unique internal configuration resisting premature failure of the internal rubber parts from the continuing on and off pressurizing that a PVB in general was not designed to endure.

Thanks! I didn't know it's not designed for continuing on and off pressurizing. But 720A won't work because it's not listed as lead free. Only 420XL and 460XL are listed as "lead free". In this case, does it mean using either 420XL or 460XL would require a frequent replacement/repair of the internal parts?